Efficiency optimization method for electric fuel combination pump based on power matching

Abstract

The present application relates to a kind of electric fuel combination pump efficiency optimization method based on power matching, including in the gear pump import pressure determined condition, according to the maximum rotational speed of the gear pump gear tooth root not cavitation formula transformation obtains the preliminary minimum import pressure of the gear pump;Using fluid mechanics calculation software, the preliminary minimum import pressure of the gear pump is corrected, obtains the optimal import pressure of the gear pump;According to the outlet pressure of centrifugal pump and the import pressure of gear pump equal principle, and in order to ensure that the centrifugal pump has enough pressure increasing capacity, the optimal import pressure of the gear pump is calculated to obtain the optimal outlet pressure of centrifugal pump corresponding to working condition, avoid the outlet pressure of centrifugal pump design too high to make power waste, to realize the improvement of combination pump efficiency.The present application makes the power input of motor into the effective power of centrifugal pump and gear pump to the greatest extent, so that the efficiency of electric fuel combination is optimal.

Description

Technical Field

[0001] This invention relates to the field of aero-engine fuel pump design technology, and in particular to a power matching calculation method for improving the efficiency of combined pumps. Background Technology

[0002] As an energy conversion device, the aviation fuel pump can convert mechanical energy into hydraulic energy to obtain fuel with a certain flow rate and pressure. Its design not only needs to provide the combustion chamber with fuel that meets certain flow rate and pressure requirements across the entire operating range, but also needs to adjust its fuel supply and pressure over a wide range, and operate reliably over a wide range of fuel temperature and ambient temperature variations.

[0003] In the field of aviation fuel pumps, centrifugal pumps are often used as backing pumps due to their simple structure, strong anti-pollution ability, and long service life, while external gear pumps are often used as main fuel pumps due to their high efficiency. As aero engines develop towards higher performance, higher requirements are placed on fuel pumps, such as high performance, long service life, and light weight. Therefore, researchers at home and abroad are not only striving to explore the potential of the two types of fuel pumps, but also conducting research on new types of fuel pumps.

[0004] Currently, an international design for aviation fuel pumps has been proposed, which integrates the fore-stage booster centrifugal pump and the main fuel gear pump into a single centrifugal gear combination pump with coaxial drive. This structure can significantly reduce the overall pump size and weight, and also simplifies the casing design, further reducing weight. Furthermore, when applied to small and medium thrust engines, an electric motor can replace the engine accessory casing to drive the fuel pump. By controlling the motor speed, the fuel flow rate can be adjusted in real time, achieving precise fuel supply on demand while avoiding the significant return oil temperature rise problem caused by traditional accessory casing drives.

[0005] Efficiency is one of the key indicators in fuel pump design. The conventional approach is to design high-efficiency centrifugal pumps and gear pumps independently, and then combine them to form a centrifugal-gear combination pump to improve the overall efficiency of the electric fuel combination pump. Although this approach is a feasible solution, it does not consider the power distribution and matching between the centrifugal pump and the gear pump from a system perspective. Since the working efficiency of the centrifugal pump and the gear pump is significantly different, the goal of achieving the optimal efficiency of the combination pump cannot be achieved without reasonable power distribution.

[0006] Existing technologies emphasize starting from a local single pump, that is, finding the design point of optimal efficiency for centrifugal pumps and gear pumps through optimization design, without taking a global perspective and considering the impact of the power matching relationship between the two pumps on the efficiency of the combined pump. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an efficiency optimization method for an electric fuel combination pump based on power matching, which can match the power of a two-stage combined pump of centrifugal pump and gear pump and improve the working efficiency of the combined pump.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an efficiency optimization method for an electric fuel combination pump based on power matching, wherein the electric fuel combination pump is composed of a coaxially driven centrifugal pump and a gear pump, the centrifugal pump being a pre-pressurization stage before the gear pump, that is, the fuel outlet pressure of the centrifugal pump enters the gear pump stage at the inlet pressure of the gear pump, and the efficiency optimization method of the combination pump includes the following steps:

[0009] Step 1: Under the condition that the inlet pressure of the gear pump is determined, the initial minimum inlet pressure p of the gear pump is obtained by transforming the formula for calculating the maximum rotational speed at which cavitation does not occur at the root of the gear teeth. gi_min The calculation formula is:

[0010]

[0011] Where, r a r f For the addendum circle radius and dedendum circle radius of the gears in the gear pump; p b Where n is the saturated vapor pressure of aviation fuel, and n is the speed of the gear pump.

[0012] Step 2: Using fluid dynamics calculation software, set the gear pump inlet pressure to the aforementioned initial minimum inlet pressure p of the gear pump. gi_min For the gear pump under the conditions of rotational speed n, temperature T, and outlet pressure p go The internal flow field under operating conditions was simulated, and the initial minimum inlet pressure p of the gear pump was determined. gi_min The adjustment is made to obtain the optimal inlet pressure p of the gear pump. gim ;

[0013] Step 3: Based on the principle that the outlet pressure of the centrifugal pump should be equal to the inlet pressure of the gear pump, and to ensure that the centrifugal pump has sufficient boosting capacity, the optimal outlet pressure p of the centrifugal pump is then determined. com With the optimal inlet pressure p of the gear pump gim A safety factor is set between them, as shown in the following formula:

[0014] p com =Sp gim

[0015] Where S is the safety factor, ranging from 1.01 to 1.05; that is, the optimal outlet pressure p of the centrifugal pump corresponding to the aforementioned operating condition is calculated. com This avoids excessively high outlet pressure in the design of centrifugal pumps, which would otherwise lead to power waste and thus improve the efficiency of the combined pump.

[0016] Furthermore, it also includes setting the optimal outlet pressure p of the centrifugal pump corresponding to the aforementioned operating condition. com The steps for designing the centrifugal pump impeller and volute are described as a design metric.

[0017] Furthermore, the mathematical expression for the maximum rotational speed at which cavitation does not occur at the root of the gear teeth under the condition that the inlet pressure of the gear pump is determined in step one is:

[0018]

[0019] Where, n max ω max The maximum speed and maximum angular velocity of the gear pump; r a r f For the addendum circle radius and dedendum circle radius of the gears in the gear pump; p b This refers to the saturated vapor pressure of aviation fuel.

[0020] Furthermore, step two specifically involves:

[0021] (21) Set the rotational speed n, temperature T and outlet pressure p of the gear pump. go The operating parameters are set, and the gear pump inlet pressure p is also set. gi The initial minimum inlet pressure p of the gear pump is... gi_min Furthermore, fluid dynamics calculation software was used to simulate the internal flow field of the gear pump under the aforementioned operating conditions based on the operating parameters.

[0022] (22) In the simulated internal flow field of the gear pump, determine in turn whether cavitation occurs at the root of the gear teeth and whether the volumetric efficiency of the gear pump is less than 80% to 90%. If at least one of the conditions is met, then set the gear pump inlet pressure p. gi Add 0.1p gi And repeat step (21); otherwise, it is assumed that the gear pump inlet pressure p is at this time. gi If the condition is met, let the gear pump inlet pressure p at this time... gi That is, the optimal inlet pressure p of the gear pump gim .

[0023] Furthermore, the fluid dynamics calculation software is a CFD software, specifically FLUENT, CFX, or PumpLinx.

[0024] The beneficial effects of this invention are: This invention solves the problem of power matching not being considered in the current design of integrated combined pumps, and provides a power matching calculation method for coaxial fuel combined pumps, which obtains the optimal outlet pressure of the centrifugal pump.

[0025] For motor-driven combined pumps, the optimal centrifugal pump outlet pressure p is directly sought. com This is quite challenging. In the design of combined pumps, the outlet pressure of the centrifugal pump is usually the inlet pressure of the gear pump. Therefore, it is necessary to find the optimal inlet pressure p of the gear pump. gim And indirectly obtain the optimal centrifugal pump outlet pressure p com This improves the efficiency of the combined pump.

[0026] Based on the above method, when designing the booster centrifugal pump for the electric fuel combination pump, the optimal centrifugal pump outlet pressure corresponding to the operating condition can be obtained through the above steps. Then, the impeller and volute of the centrifugal pump and other flow-through components can be designed according to the pressure value. The above design idea and design steps can achieve a suitable power match between the centrifugal pump and the gear pump, and can maximize the efficiency of the electric fuel combination pump at the system level.

[0027] In addition, the present invention uses simulation to significantly shorten the design cycle and proposes a new design index for the design of electric fuel combination pumps. That is, when designing the booster centrifugal pump, it is necessary to meet the optimal inlet pressure of the centrifugal pump corresponding to the operating parameters. This can achieve a suitable power matching between the two pumps, so that the power input by the motor can be converted into the effective power of the centrifugal pump and the gear pump to the greatest extent, thereby optimizing the efficiency of the electric fuel combination. Attached Figure Description

[0028] Figure 1 This is a flowchart of the method of the present invention;

[0029] Figure 2 This is a flowchart illustrating the modification of the initial minimum inlet pressure of the gear pump according to the present invention. Detailed Implementation

[0030] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0031] The optimal centrifugal pump outlet pressure p of the electric fuel combination pump of centrifugal pump and gear pump com The challenge was significant, so the inventors first analyzed the characteristics of the combined pump to determine the research path for this invention: how to effectively optimize the efficiency of the combined pump. The specific analysis is as follows:

[0032] The power distribution of this combined pump is shown in equation (1). Part of the input power from the electric motor acts on the centrifugal pump and gear pump to generate fuel with a certain flow rate and pressure, while the other part becomes ineffective power in different forms, resulting in power loss. The power acting on the centrifugal pump and gear pump to generate fuel with a certain flow rate and pressure is the effective output power. Therefore, the formula for calculating the efficiency of the electric fuel combined pump is shown in equation (2):

[0033] P in =P e =P c +P g +P w (1)

[0034]

[0035] Among them, P in P is the input power of the combined pump. e P represents the output power of the electric motor. c P is the effective output power of the centrifugal pump. g P is the effective output power of the gear pump. w η represents ineffective power; η is the efficiency of the electric fuel combination pump.

[0036] The effective output power of an oil pump is equal to the product of its input power and its efficiency. The input power is, in turn, equal to the product of the pump's boost pressure and its theoretical flow rate. Therefore, the effective output powers of centrifugal pumps and gear pumps are respectively:

[0037]

[0038] Where, q c q represents the theoretical flow rate of the centrifugal pump. g Δp is the theoretical flow rate of the gear pump. c Δp is the boost pressure value of the centrifugal pump. g η is the boost pressure value of the gear pump. c The efficiency of the centrifugal pump; η g This refers to the efficiency of the gear pump.

[0039] Because the two pumps are connected in series, the output flow and return oil flow of the centrifugal pump are both concentrated at the outlet of its volute, supplying the inlet of the gear pump. Therefore, the theoretical flow rates of the centrifugal pump and the gear pump are equal, i.e.:

[0040] q = q c =q g (4)

[0041] Where q is the theoretical flow rate of the centrifugal pump and gear pump.

[0042] The boost pressure of the oil pump is equal to the difference between its outlet and inlet pressures. Since the centrifugal pump acts as a pre-stage booster pump for the gear pump, its outlet pressure equals the gear pump's inlet pressure. Therefore, the boost pressure values ​​for both the centrifugal and gear pumps are:

[0043]

[0044] Where, p co p is the outlet pressure of the centrifugal pump. ci p is the inlet pressure of the centrifugal pump. go p is the outlet pressure of the gear pump. gi This refers to the inlet pressure of the gear pump.

[0045] Substituting equations (3), (4), and (5) into equation (2), we get:

[0046]

[0047] Considering the operating conditions of the electric fuel pump, typically under a specific operating condition, the theoretical flow rate q and the electric motor output power P are... e Centrifugal pump inlet pressure p ci and gear pump outlet pressure p go For a fixed value, the centrifugal pump efficiency η c and gear pump rate η g Generally related to the design structure, and based on the design, it is usually within a small, specific range, therefore assumed to be a constant value. Thus, the method to improve the efficiency of the combined pump under a certain operating condition is to find the optimal centrifugal pump outlet pressure p. co This maximizes the value of equation (6). The efficiency of a centrifugal fuel pump is typically lower than that of a gear pump across the entire operating range (especially during engine cruise). Therefore, when the centrifugal pump outlet pressure p... co When the value decreases, the molecule of equation (6) increases.

[0048] However, the outlet pressure of a centrifugal pump cannot be reduced indefinitely. This is because, as a booster pump, a centrifugal pump needs to provide a certain pressure to the gear pump. When the pressure is lower than a certain critical value, cavitation will occur at the root of the gear pump teeth, damaging the gears and side plates. Furthermore, excessively low pressure will affect the fuel filling at the inlet of the gear pump, resulting in a reduction in the volumetric efficiency of the gear pump.

[0049] In summary, the method for achieving appropriate power matching between centrifugal pumps and gear pumps to improve the efficiency of electric fuel combination pumps aims to find an optimal centrifugal pump outlet pressure, denoted as the optimal centrifugal pump outlet pressure p. com This pressure must satisfy the following two constraints:

[0050] 1. As small as possible;

[0051] 2. Meet the centrifugal pump boosting function, that is, ensure that no cavitation occurs at the root of the gear teeth of the gear pump and ensure that the volumetric efficiency of the gear pump meets 80% to 90%.

[0052] To achieve the above objectives, the present invention provides the following specific embodiments:

[0053] Example 1: As Figure 1-2 As shown, an efficiency optimization method for an electric fuel combination pump based on power matching is disclosed. The electric fuel combination pump consists of a coaxially driven centrifugal pump and a gear pump. The centrifugal pump is a pre-pressurization stage before the gear pump, meaning that the fuel outlet pressure of the centrifugal pump enters the gear pump stage at the inlet pressure of the gear pump. The efficiency optimization method for this combination pump includes the following steps:

[0054] Step 1: Under the condition that the inlet pressure of the gear pump is determined, the mathematical expression for the maximum rotational speed at which cavitation does not occur at the root of the gear teeth is:

[0055]

[0056] Where, n max ω max The maximum speed and maximum angular velocity of the gear pump; r a r f For the addendum circle radius and dedendum circle radius of the gears in the gear pump; p b The saturated vapor pressure of aviation fuel;

[0057] The initial minimum inlet pressure p of the gear pump is obtained by transforming the mathematical expression of the maximum rotational speed at which cavitation does not occur at the root of the gear teeth. gi_min The calculation formula is:

[0058]

[0059] Where, r a r f For the addendum circle radius and dedendum circle radius of the gears in the gear pump; p b Where n is the saturated vapor pressure of aviation fuel, and n is the speed of the gear pump.

[0060] Step 2: Using fluid dynamics calculation software, set the gear pump inlet pressure to the aforementioned initial minimum inlet pressure p of the gear pump. gi_min The gear pump's rotational speed n, temperature T, and outlet pressure p go The internal flow field under operating conditions was simulated, and the initial minimum inlet pressure p of the gear pump was determined. gi_min The adjustment is made to obtain the optimal inlet pressure P of the gear pump. gim ;

[0061] The specific correction steps are as follows:

[0062] (21) Set the rotational speed n, temperature T and outlet pressure p of the gear pump. go The operating parameters are set, and the gear pump inlet pressure p is also set. gi The initial minimum inlet pressure p of the gear pump is... gi_min The internal flow field of the gear pump under the aforementioned operating conditions is simulated using fluid dynamics calculation software based on the aforementioned operating parameters. The fluid dynamics calculation software is a CFD software, specifically FLUENT, CFX, or PumpLinx.

[0063] (22) In the simulated internal flow field of the gear pump, determine in turn whether cavitation occurs at the root of the gear teeth and whether the volumetric efficiency of the gear pump is less than 80% to 90%. If at least one of the conditions is met, then set the gear pump inlet pressure p. gi Add 0.1p gi And repeat step (21); otherwise, it is assumed that the gear pump inlet pressure p is at this time. gi If the condition is met, let the gear pump inlet pressure p at this time... gi That is, the optimal inlet pressure p of the gear pump gim .

[0064] Step 3: Based on the principle that the outlet pressure of the centrifugal pump should be equal to the inlet pressure of the gear pump, and to ensure that the centrifugal pump has sufficient boosting capacity, the optimal outlet pressure p of the centrifugal pump is then determined. com With the optimal inlet pressure P of the gear pump gim A safety factor is set between them, as shown in the following formula:

[0065] p com =Sp gim

[0066] Where S is the safety factor, ranging from 1.01 to 1.05; that is, the optimal outlet pressure p of the centrifugal pump corresponding to the aforementioned operating condition is calculated. com ;

[0067] Step 4: Set the optimal outlet pressure p of the centrifugal pump to... com The steps for designing the centrifugal pump impeller and volute are described as a design metric.

[0068] This patent proposes a power matching method for the high-efficiency design of a certain type of electric fuel combination pump. The operating parameters of the combination pump are shown in the table, and the specific calculation process is as follows:

[0069] Table 1 Operating parameters of a certain type of electric fuel combination pump

[0070] Operating parameters Parameter value Rotational speed (r / min) 15000 Temperature (°C) 100 Gear pump outlet pressure (MPa) 10

[0071] (1) Calculate the initial minimum inlet pressure of the gear pump:

[0072] Using the formula given in step one, the initial minimum inlet pressure of the gear pump under the design conditions is calculated as follows:

[0073]

[0074] (2) Simulation and correction of the initial minimum inlet pressure: The gear pump speed n, temperature T and outlet pressure p shown in Table 1 are adjusted. go The internal flow field of the operating conditions was simulated, and the initial minimum inlet pressure p of the gear pump was calculated. gi_min After correction, the optimal inlet pressure of the gear pump is found to be 0.375 MPa.

[0075] (3) Determine the optimal inlet pressure of the centrifugal pump:

[0076] Taking a correction factor of 1.02, the optimal outlet pressure of the centrifugal pump corresponding to the design operating condition is determined using the formula given in step three: p com =Sp gim =0.383MPa

[0077] The optimal outlet pressure p of the centrifugal pump corresponding to the operating conditions described in Table 1 was obtained through the above process. com Furthermore, this pressure was used as a design indicator for the centrifugal pump impeller and volute, achieving a suitable power match between the centrifugal pump and gear pump, and realizing a high-efficiency design for a certain type of electric fuel combination pump.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the efficiency of an electric fuel combination pump based on power matching, characterized in that, The electric fuel combination pump consists of a coaxially driven centrifugal pump and a gear pump. The centrifugal pump is a booster stage before the gear pump, meaning that the fuel outlet pressure of the centrifugal pump enters the gear pump stage at the inlet pressure of the gear pump. The efficiency optimization method for this combination pump includes the following steps: Step 1: Under the condition that the inlet pressure of the gear pump is determined, the initial minimum inlet pressure of the gear pump is obtained by transforming the formula for calculating the maximum rotational speed at which cavitation does not occur at the root of the gear teeth. The calculation formula is: ， in, , For the addendum circle radius and dedendum circle radius of the gears in the gear pump; Where n is the saturated vapor pressure of aviation fuel, and n is the speed of the gear pump. Step 2: Using fluid dynamics calculation software, set the gear pump inlet pressure to the aforementioned initial minimum inlet pressure of the gear pump. For the gear pump under the conditions of rotational speed n, temperature T, and outlet pressure p go The internal flow field under operating conditions was simulated to determine the initial minimum inlet pressure of the gear pump. The adjustment is made to obtain the optimal inlet pressure of the gear pump. Specifically: (21) Set the rotational speed n, temperature T and outlet pressure of the gear pump. The operating parameters are set, and the gear pump inlet pressure p is also set. gi The initial minimum inlet pressure of the gear pump is... Furthermore, fluid dynamics calculation software was used to simulate the internal flow field of the gear pump under the specified operating conditions based on the operating parameters. (22) In the simulated internal flow field of the gear pump, determine in turn whether cavitation occurs at the root of the gear teeth and whether the volumetric efficiency of the gear pump is not 80%~90%. If at least one of the conditions is met, then set the gear pump inlet pressure p gi Add 0.1p gi And repeat step (21); otherwise, it is assumed that the gear pump inlet pressure p is at this time. gi If the condition is met, let the gear pump inlet pressure p at this time... gi This is the optimal inlet pressure for the gear pump. ; Step 3: Based on the principle that the outlet pressure of the centrifugal pump should be equal to the inlet pressure of the gear pump, and to ensure that the centrifugal pump has sufficient boosting capacity, the optimal outlet pressure of the centrifugal pump is then determined. With the optimal inlet pressure of the gear pump A safety factor is set between them, as shown in the following formula: ， Where S is the safety factor, ranging from 1.01 to 1.05; that is, the optimal outlet pressure of the centrifugal pump corresponding to the aforementioned operating condition is calculated. This avoids excessively high outlet pressure in the design of centrifugal pumps, which would otherwise lead to power waste and thus improve the efficiency of the combined pump.

2. The method for optimizing the efficiency of an electric fuel combination pump based on power matching as described in claim 1, characterized in that, It also includes the optimal outlet pressure of the centrifugal pump corresponding to the aforementioned operating condition. The steps for designing the centrifugal pump impeller and volute are described as a design metric.

3. The method for optimizing the efficiency of an electric fuel combination pump based on power matching as described in claim 1, characterized in that, In step one, under the condition that the inlet pressure of the gear pump is determined, the mathematical expression for the maximum rotational speed at which cavitation does not occur at the root of the gear teeth is: ， in, , These are the maximum speed and maximum angular velocity of the gear pump; , For the addendum circle radius and dedendum circle radius of the gears in the gear pump; This refers to the saturated vapor pressure of aviation fuel.

4. The method for optimizing the efficiency of an electric fuel combination pump based on power matching as described in claim 1, characterized in that, The fluid dynamics calculation software is a CFD software, specifically FLUENT, CFX, or PumpLinx.

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